INTERFACE SELECTION
The SPC has two built-in interfaces; the USB and parallel interfaces. The interface in use is
selected automatically.
n Automatic selection
When the Stylus Scan is turned on, it initializes and then goes into an idle state. During
this idle period the printer scans the interfaces for incoming data. The interface that
receives data first is selected.
When the host stops transferring data and the printer is in the stand-by state for a
certain amount of time, the printer returns to the idle state. As long as the host sends
data or the printer interface is in the busy state, the interface selection does not change.
n Interface status and selection
When the parallel interface is not selected, the interface goes into the busy state. When
the printer initializes or returns to the idle state, the parallel interface goes into the
ready state. Be aware that an interrupt signal such as the -INIT signal only takes effect
on the parallel interface when the parallel interface is selected.
IEEE1284.4 PROTOCOL
The packet protocol described by IEEE1284.4 standard allows a device to carry on multiple
exchanges or conversations which contain data and/or control information with another
device at the same time across a single point-to-point link. The protocol is not, however, a
device control language. It does provide basic transport-level flow control and multiplexing
services. The multiplexed logical channels are independent of each other and blocking of
one has no effect on the others. The protocol operates over IEEE1284.
o Automatic Selection
An initial state is compatible interface and starts IEEE1284.4 communication
when magic strings (1284.4 synchronous commands) are received.
o On
An initial state is IEEE1284.4 communication and data that received it by the time
it is able to take synchronization by magic string (1284.4 synchronous commands)
is discarded.
o Off
An initial state is compatible interface and never starts IEEE1284.4
communication even if magic strings (1284.4 synchronous commands) are
received.
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